1. Field of the Invention
The present invention relates to a technology for monitoring the sealing performance of a control panel of a machine tool.
2. Description of the Related Art
Generally, machine tools are placed under adverse surrounding environments (cutting fluid mist, dust, fine particles, or the like). Since electrical components such as breakers and integrated circuits are mounted in the control panels of the machine tools, the control panels need to protect the electrical components from the surrounding environments.
In many cases, the control panels of machine tools employ sealing structures using packing or sealing. However, there is a likelihood that the sealing performance of the control panels is impaired due to aged deterioration, modifications for upgrading the control panels (placement of jigs or peripheral devices), or the like.
Conventionally, as methods for confirming the sealing performance of control panels, there have been known a method in which visual confirmation is performed when a door is opened and a method in which a vapor amount or absolute humidity is calculated from temperature and humidity data. Japanese Patent Application Laid-open No. 10-153515 describes a technology in which temperature and humidity inside a sealing container are measured by sensors to calculate a vapor amount as an amount that does not depend on temperature and the calculated vapor amount is compared with a reference amount to detect the sealing performance of the container.
In addition, Japanese Patent Application Laid-open No. 2003-240666 describes a technology in which temperature and humidity inside and outside the panel of a housing are measured and the difference between a vapor amount inside the panel and a vapor amount outside the panel is monitored to detect the sealing performance of the housing.
However, it is not possible to quantitatively determine the sealing performance with the visual confirmation. Further, according to the technology described in Japanese Patent Application Laid-open No. 10-153515, a sensitivity for determining sealing is made different or the determination of the sealing becomes impossible depending on seasons at which a sealing state is produced since a vapor amount is large in summer and small in winter. In addition, since the technology employs a method in which a calculated vapor amount is compared with a reference amount, a vapor amount inside a panel becomes equal to a vapor amount outside the panel when the control panel of a machine tool is opened for maintenance or the like, which results in a false determination that the sealing performance has been impaired. That is, it is not possible to distinguish a case in which the door of the control panel has been opened from a case in which the sealing performance has been impaired due to any other reasons.
Further, since the technology described in Japanese Patent Application Laid-open No. 2003-240666 needs a temperature sensor and a humidity sensor outside the panel, it is costly and needs places to install the sensors. In addition, since the technology employs a method in which a vapor amount inside the panel is compared with a vapor amount outside the panel, it is falsely determined, as in the technology described in Japanese Patent Application Laid-open No. 10-153515, that the sealing performance has been impaired when the door of the control panel of the machine tool is opened/closed for maintenance or the like and a vapor amount inside the panel becomes equal to a vapor amount outside the panel.